I think I might see the issue. Jeff, I'm assuming you're using a
developer build of Open MPI with GNU, Intel, or Pathscale compilers,
right? At least someone below was using PGI. The first three
compilers on a developer build have the magic pixie dust arguments
added that makes calling an undeclared function an error. PGI, Sun
Workshop, and non-developer builds don't have that pixie dust. So
it's not an error to call an undeclared function in those cases, and
AC_COMPILE_IFELSE won't error out. AC_LINK_IFELSE should always be
used to check for functions for precisely that reason.